Abstract:

【Objective】In active dune fields, the transition zones between active dunes and interdune lowlands, which have high temporal and spatial heterogeneity and complex ecological processes, can indicate or coordinate the relative relationship between vegetation and sand dune and regulate the area and structure of vegetation in the whole active sand dunes. In the last few decades, much attention has been paid to the vegetation processes in active sand dunes or interdune lowlands, while researches on how vegetation establishes and develops in transition zones between active dunes and dune slacks are still scarce. Most of all, study on temporal and spatial patterns, vegetation composition, plant adaptation mechanism and the restrictive factors in transition zones between active dune and interdune lowland is not still reported. 【Method】In this paper, by means of the belt transect method in the field investigation, we measured the height and width of sand burial on leeward slopes of active sand dunes as well as the depth of wind erosion on windward slopes of active sand dunes at Wulanaodu region, the western Horqin Sandy Land, and examined the plant richness and abundance in the quadrats by the end of growing seasons. We especially investigated the effects of transition zone dynamics on vegetation areas and patterns in interdune lowlands. Through this study, we aim at answering two questions that how aeolian erosion and sand burial influence the temporal and spatial patterns of the transition zones between active dunes and interdune lowlands and that how the transition zone dynamics affect vegetation areas and patterns in whole active dune fields. 【Result】The result showed that (1) part of Limnocryptophyte-meadow and Steppe species in interdune lowlands retreated from the transition zones in leeward slopes and part of pioneer vegetative propagation was dominant in frequency and density in the transition zones of windward slopes due to the dynamic changes of the transition zone between active dune and interdune lowland. The width of the transition zones on leeward slopes was 4-6 m, and the width of the transition zones on windward slopes was 3-5 m, indicating that the transition zones belonged to fine-scale ones. The transition zones on leeward slopes formed in late May, and the ones on windward slopes formed in late September. (2) There were significant and positive (P < 0.05) correlations between the widths of transition zones from leeward slopes of active sand dunes to interdune lowlands and the areas of interdune lowlands or the perpendicular widths to the wind direction; the the widths of transition zones from windward slopes of active sand dunes to interdune lowlands were not significantly (P > 0.05) correlated with the areas of interdune lowlands or the perpendicular widths to the wind direction, but was significantly and positively (P < 0.05) correlated with the widths of increased vegetation of interdune lowlands. (3) In the active sand dune field, the vegetation-covered areas had an increasing trend. (4) In the large area (> 5 hm²) of the interdune lowland, the width of the vertical wind direction was large, and vegetation had high density and was high, and thus was able to form large-area windbreaks and lower wind speeds, leading to low speeds of sand burial in the leeward slope and rapid speeds of plant invasion in the windward slope, hence, increase the vegetation width and area in the interdune lowlands of active sand dune fields. 【Conclusion】This study indicated that in natural conditions, vegetation restoration of active sand dune fields generally commences with revegetation of transition zones between windward slopes of active sand dunes and interdune lowlands; and the interdune lowlands of large area play an important role during vegetation restoration of active sand dune fields.

Key words: aeolian erosion, sand burial, transition zone, interdune lowland, vegetation restoration